A cofferdam is a watertight enclosure that is dewatered (e.g., pumped dry) to facilitate work below a surface of a body of water. Cofferdams may be used, for example, in connection with inspection, maintenance, demolition, and/or construction of civil engineering projects such as bridges, walkways, or dams that includes a component that extends from on or below the floor of a body of water. Cofferdams may also be used in the repair of ships.
Construction of cofferdams for civil engineering projects may begin with the dredging of soil and/or soft sediment from an area on which the cofferdam is to be constructed. Some cofferdams may then be constructed by driving sheet piles into the floor of the body of water around a worksite. The tops of the sheet piles extend above the surface of the body of water after the bottoms of the sheet piles have been driven into the floor of the body of water. The sheet piles are connected together, for example by interconnecting, to form a wall enclosing the sides of the worksite. Internal bracing and tying are applied as needed. An underwater concrete soil course can be poured into the cofferdam to seal the bottom from water entry. The watertight enclosure is then dewatered to provide a dry environment in which work can be performed. Other cofferdams may be constructed by filling vinyl tubes with water. The vinyl tubes may rest on the floor of the body of water and have a height that is greater than the surface of the body of water, thus giving an overall negative buoyancy to the filled vinyl tubes. The worksite may be surrounded by such water-filled vinyl tubes to form a watertight enclosure. The weight of each filled vinyl tube holds the tube in place on the floor of the body of water. Again, watertight enclosure is then dewatered to provide a dry environment in which work can be performed.
Cofferdams, such as those used to surround or partially surround a worksite have a drawback in that they contact, disturb, and/or penetrate the floor of the body of water by being driven into and/or resting on the floor of the body of water. A type of cofferdam that can be used to surround or partially surround a worksite without contacting, disturbing, and/or penetrating the floor of the body of water surrounding the worksite is desirable.